Described below is a method for allocating resources to frequency bands of a radio communication system as well as a corresponding network device and user station.
Future mobile radio communication systems are intended to allow both short-range and long-range transmissions between a central base station and mobile stations. For the short range it is advantage to use what is known as time division duplex (TDD), as this procedure allows channel estimation in the downlink DL from transmissions in the uplink UL due to the reciprocity of the radio channel. This is an important feature for example for what are known as MIMO systems (MIMO: Multiple Input Multiple Output Antennas) with spatial multiplexing or for what are known as multi-hop networks.
As spatial multiplexing SMUX requires channel estimation with a high level of accuracy and signal to noise ratios higher than around 11 dB, spatial multiplexing is currently considered to be a typical short-range technology for transmissions up to around 200 m. If TDD is used together with spatial multiplexing in a limited number of hotspots, spatial separation between different hotspots prevents the generally known interference between base stations, which is seen as a major disadvantage of TDD.
For cellular long-range systems frequency division duplex (FDD) is preferred due to its clearly defined interference conditions. FDD can be used as full duplex with a diplexer filter (diplexer/antenna separator filter) to separate transmissions in the downlink and uplink. Alternatively FDD can be used as half duplex, with each mobile station either only sending or only receiving in a respective time slot, such that a switch together with a fast-control local oscillator can replace the diplexer. Instead of a fast-control oscillator it is also possible with half-duplex FDD to switch between the lower and upper frequency band or sideband. This allows more economical oscillator solutions.
Proposals for converting TDD, FDD and half-duplex FDD as well as possible combinations thereof are the subject of general discussion.
GB 2 398 455 A describes TDD operation in an FDD band. The available resources of a first of two FDD frequency bands are thereby divided into time slots and allocated symmetrically for TDD uplinks and TDD downlinks. The FDD frequency band is a frequency band generally used as an FDD uplink frequency band. The assigned duplex frequency band, in other words an FDD downlink frequency band, is also used as required expressly only for TDD downlinks to prevent interference. With this procedure therefore TDD transmissions are implemented instead of FDD transmissions in a duplex-FDD frequency band.